a DE is only as powerful as the human sat in front of it who configured it. In normal daily use many of us only use a tiny percentage of the features available to us. I'm still finding new tricks with MATE too. glad you found something you like though with fvwm.

You are correct that every use case is different and i also think that these window managers are becoming old as newer tech like wayland arrives. MATE is in transition state like GNOME3 is since F14. I am waiting for full transition to complete. Have one machine for MATE and one for XFCE. I do not fully understand the implications of the changes.

the transition is from GTK+2 to GTK+3 started with Fedora 23 and in F25 it is 99.9% complete. all packages are compiled in GTK+3 for this release. sure there are a few niggles that still need ironing out but it works reasonably well as a DE. The stumbling blocks I have faced are due to components from other DE I use (bluez from GNOME in particular).